The invention relates to a procedure for dimensionally accurate sintering of a shaped piece manufactured from a blank consisting of a porous ceramic material, especially a dental bridge, in which the shaped piece during sintering remains connected with a support via at least a first connection like a rib, which is manufactured from the blank. The invention also makes reference to a residual blank as a part of a blank consisting of a porous ceramic material with a shaped piece manufactured by removal of material from the blank that is connected integrally with the residual blank.
A procedure of this type is known from EP-B-1 154 969. To prevent during sintering of the shaped piece, which consists of a ceramic material, movement of the shaped piece relative to a base due to the reduction in volume (shrinkage), provision is to brace the shaped piece on a movable support such as a holding rib or on rollers. The possibility also exists to connect the shaped piece and the rib projecting in integral fashion from it with a burner base that is manufactured together with the shaped piece from a blank by materials removal. With a bridge having multiple members, from each bridge member a rib projects outward.
This has a disadvantage in that if the base is deformed, the alteration in geometry can be transferred to only one of the members, with the possibility that the members can move relative to each other, and the shape can change in undesired fashion.
WO-A-99/47065 and WO-A-02/45614 relate to dental bridges that are manufactured through sintering from blanks consisting of porous ceramic material. For this, the blank is accommodated by a frame to produce the bridge by milling. First the bridge is connected via ribs with the residual blank remaining from the blank, which ribs are separated when the processing is completed. The separation spots are then ground smooth. Then the sintering takes place.
From WO-A-2005/051220, a procedure is known for manufacturing a crown as a shaped piece. With this procedure, the shaped piece is processed out of a blank, and before releasing the shaped piece from the blank, it remains connected to the residual blank via one or more ribs, which then are cut through. Then a sintering through occurs.